Microchemical method and apparatus for synthesis and coating of colloidal nanoparticles

Abstract

The present invention represents a radical departure from most conventional macro-scale batch processing methods employed to synthesize and coat colloidal nanoparticles. Synthesis and coating are in series and in-situ, obviating the need for numerous cumbersome, and often expensive intermediate-processing steps. In one embodiment, the invention is a method and apparatus for synthesizing colloidal nanoparticles. In another embodiment, the invention is a method and apparatus for enabling coating of colloidal nanoparticles using an electrophoretic switch for contacting and separating said colloid nanoparticles.

Description

FIELD OF THE INVENTION The present invention relates generally to microfluidic chemical systems for synthesis and coating of colloidal nanoparticles. In particular, the invention accomplishes continuous synthesis of colloidal nanoparticles and in-situ coating of their surfaces with various functionalities, through novel reactant-contacting schemes. BACKGROUND OF THE INVENTION Colloidal nanoparticles have innumerable applications in almost all fields of science, and are ubiquitous in materials science, chemistry and biology. Industrial applications of colloidal spheres of silica and titania, for example, include adhesion and lubrication technology, pigments, catalysis, thin films for photovoltaic, electrochromic, photochromic, electroluminescent devices, sensors, foods, health-care, anti-reflective coatings, chromatography, ceramics, optoelectronics, photonic band-gap (PBG) materials, etc. Further applications are applicable when the surfaces of the particles are modified or coated...

AI Technical Summary

Benefits of technology

Microchemical systems offer potential advantages both in the ability to synthesize colloids, tune their surface properties, composition and crystallinity and in the ability to control their self-assembly as a route to materials synthesis on multiple length scales. As used herein, the term “nanoparticle” encompasses particles ranging in size from as small as about one nanometer to as large as several hundred nanometers in diameter. The ability to integrate these functions into a single device gives a powerful platform for the discovery, screening and analysis of novel materials. In one embodiment, the invention relates to a microreactor and a method for synthesizing colloidal nanoparticles using the microreactor. The microreactor has at least one inlet channel; at least one micromixing block positioned downstream from the at least one inlet channel; an aging section positioned downstream from the at least one micromixing block channel where the nanoparticles can grow to their final size; and at least one outlet channel positioned downstream from said aging section.

Utilizing the apparatus of the invention structures can be realized that cannot be obtained with conventional macroscale technology. For example, heat and mass transfer is expedited in the microscale apparatus of the invention such that more aggressive processing conditions that are not feasible on a macroscopic scale may be used. In addition, the size of the nanoparticle formed can be controlled by the size of the microchannels. An electrophoretic switch can be used to purify nanoparticles which eliminates the need for cumbersome wash and centrifugation steps. Finally, the apparatus of the invention enables continuous multi-step particle processing, that is extremely difficult to achieve using macroscale techniques.

Problems solved by technology

Applying coating techniques for nanoparticles involves difficulties which do not exist in coating processes of flat surfaces, due to the differential physical characteristics of spherical systems.

Techniques applied to the preparation of a coating for a spherical surface currently involve numerous cumbersome, and often expensive, intermediate-processing steps.

These steps involve multiple washings and centrifugations, and often degrade particle quality.

Also, intermediate steps like sintering can profoundly affect the surface character of the particles being processed.

In addition, due to the number of processing steps involved in coating nanoparticles, conventional techniques typically must be carried out in batches.

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